There have been conventionally studied surface treatment methods such as metal coating, nonmetal coating, and chemical conversion coating. So far, various functional composite materials have been created using a matrix of a metal provided on a surface thereof with a film of another metal.
Plating is one of typical examples of the several surface treatment methods. This plating technique is widely utilized in various industries. However, such a film of a metal or the like to be formed by plating as described above is not sufficiently adhesive to the matrix unless the matrix is appropriately selected. For example, silicon, which is most widely used in the fields of semiconductor, MEMS, and the like, is one of the matrices to be provided with a metal film by plating. However, as having been pointed out, silicon generally has poor adhesion with a plated metal (Patent Document 1, for example).
As one of techniques for improving adhesion of a metal film to silicon, there is disclosed a method of immersing a surface of polycrystalline silicon in a heated aqueous solution of sodium hydroxide (NaOH) to provide unevenness in order to improve adhesion of the surface with a plated metal film (see Patent Document 2). Also disclosed is a technique of forming a porous layer with use of a special substrate and filling pores in the porous layer with a plating material by displacement plating (Patent Document 3).
Non-Patent Document 1: K. Ito and one other, “Nanohole Patterned Media”, Journal FUJITSU, Fujitsu Limited, January 2007, Vol. 58, No. 1, pp. 90-98
Non-Patent Document 2: S. Yae and four others, “Electrochemistry Communications”, August 2003, Vol. 5, p. 632
Non-Patent Document 3: K. Tsujino and one other, “Electrochemica Acta”, Nov. 20, 2007, Vol. 53, p. 28
Patent Document 1: Japanese Unexamined Patent Publication No. 2004-193337
Patent Document 2: Japanese Unexamined Patent Publication No. S60-4271
Patent Document 3: Japanese Unexamined Patent Publication No. 2006-342402
Patent Document 4: Japanese Unexamined Patent Publication No. S57-105826
Patent Document 5: Japanese Unexamined Patent Publication No. H11-283829
Patent Document 6: Japanese Unexamined Patent Publication No. 2003-288712
Patent Document 7: Japanese Unexamined Patent Publication No. 2004-237429
Patent Document 8: Japanese Unexamined Patent Publication No. 2005-139376
Patent Document 9: Japanese Unexamined Patent Publication No. 2007-533983
Patent Document 10: United States Unexamined Patent Publication No. 2005/0101153